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locking/lockdep: Reuse lock chains that have been freed

Browse source 
A previous patch introduced a lock chain leak. Fix that leak by reusing
lock chains that have been freed.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20190214230058.196511-16-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Bart Van Assche 2019-02-14 15:00:50 -08:00 committed by Ingo Molnar
parent 527af3ea27
commit de4643a773
1 changed files with 37 additions and 20 deletions
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57
kernel/locking/lockdep.c
View file

@ -292,9 +292,12 @@ static LIST_HEAD(free_lock_classes);
/**
* struct pending_free - information about data structures about to be freed
* @zapped: Head of a list with struct lock_class elements.
* @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
* are about to be freed.
*/
struct pending_free {
struct list_head zapped;
DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
};
/**
@ -2096,8 +2099,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
return 0;
}
static unsigned long nr_lock_chains;
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
int nr_chain_hlocks;
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
@ -2236,12 +2239,25 @@ static int check_no_collision(struct task_struct *curr,
*/
long lockdep_next_lockchain(long i)
{
return i + 1 < nr_lock_chains ? i + 1 : -2;
i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
return i < ARRAY_SIZE(lock_chains) ? i : -2;
}
unsigned long lock_chain_count(void)
{
return nr_lock_chains;
return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
}
/* Must be called with the graph lock held. */
static struct lock_chain *alloc_lock_chain(void)
{
int idx = find_first_zero_bit(lock_chains_in_use,
ARRAY_SIZE(lock_chains));
if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
return NULL;
__set_bit(idx, lock_chains_in_use);
return lock_chains + idx;
}
/*
@ -2260,11 +2276,6 @@ static inline int add_chain_cache(struct task_struct *curr,
struct lock_chain *chain;
int i, j;
/*
* Allocate a new chain entry from the static array, and add
* it to the hash:
*/
/*
* The caller must hold the graph lock, ensure we've got IRQs
* disabled to make this an IRQ-safe lock.. for recursion reasons
@ -2273,7 +2284,8 @@ static inline int add_chain_cache(struct task_struct *curr,
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
chain = alloc_lock_chain();
if (!chain) {
if (!debug_locks_off_graph_unlock())
return 0;
@ -2281,7 +2293,6 @@ static inline int add_chain_cache(struct task_struct *curr,
dump_stack();
return 0;
}
chain = lock_chains + nr_lock_chains++;
chain->chain_key = chain_key;
chain->irq_context = hlock->irq_context;
i = get_first_held_lock(curr, hlock);
@ -4208,7 +4219,8 @@ void lockdep_reset(void)
}
/* Remove a class from a lock chain. Must be called with the graph lock held. */
static void remove_class_from_lock_chain(struct lock_chain *chain,
static void remove_class_from_lock_chain(struct pending_free *pf,
struct lock_chain *chain,
struct lock_class *class)
{
#ifdef CONFIG_PROVE_LOCKING
@ -4246,6 +4258,7 @@ static void remove_class_from_lock_chain(struct lock_chain *chain,
* hlist_for_each_entry_rcu() loop is safe.
*/
hlist_del_rcu(&chain->entry);
__set_bit(chain - lock_chains, pf->lock_chains_being_freed);
if (chain->depth == 0)
return;
/*
@ -4254,22 +4267,19 @@ static void remove_class_from_lock_chain(struct lock_chain *chain,
*/
if (lookup_chain_cache(chain_key))
return;
if (WARN_ON_ONCE(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
new_chain = alloc_lock_chain();
if (WARN_ON_ONCE(!new_chain)) {
debug_locks_off();
return;
}
/*
* Leak *chain because it is not safe to reinsert it before an RCU
* grace period has expired.
*/
new_chain = lock_chains + nr_lock_chains++;
*new_chain = *chain;
hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key));
#endif
}
/* Must be called with the graph lock held. */
static void remove_class_from_lock_chains(struct lock_class *class)
static void remove_class_from_lock_chains(struct pending_free *pf,
struct lock_class *class)
{
struct lock_chain *chain;
struct hlist_head *head;
@ -4278,7 +4288,7 @@ static void remove_class_from_lock_chains(struct lock_class *class)
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
head = chainhash_table + i;
hlist_for_each_entry_rcu(chain, head, entry) {
remove_class_from_lock_chain(chain, class);
remove_class_from_lock_chain(pf, chain, class);
}
}
}
@ -4317,7 +4327,7 @@ static void zap_class(struct pending_free *pf, struct lock_class *class)
class->name);
}
remove_class_from_lock_chains(class);
remove_class_from_lock_chains(pf, class);
}
static void reinit_class(struct lock_class *class)
@ -4383,6 +4393,12 @@ static void __free_zapped_classes(struct pending_free *pf)
reinit_class(class);
list_splice_init(&pf->zapped, &free_lock_classes);
#ifdef CONFIG_PROVE_LOCKING
bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
#endif
}
static void free_zapped_rcu(struct rcu_head *ch)
@ -4623,6 +4639,7 @@ void __init lockdep_init(void)
#ifdef CONFIG_PROVE_LOCKING
+ sizeof(lock_cq)
+ sizeof(lock_chains)
+ sizeof(lock_chains_in_use)
+ sizeof(chain_hlocks)
#endif
) / 1024